Moisture transport system for contact electrocoagulation

ABSTRACT

An apparatus and method for use in performing ablation or coagulation of organs and other tissue includes a metallized fabric electrode array which is substantially absorbent and/or permeable to moisture and gases such as steam and conformable to the body cavity. The array includes conductive regions separated by insulated regions arranged to produce ablation to a predetermined depth. Following placement of the ablation device into contact with the tissue to be ablated, in RF generator is used to deliver RF energy to the conductive regions and to thereby induce current flow from the electrodes to tissue to be ablated. As the current heats the tissue, moisture (such as steam or liquid) leaves the tissue causing the tissue to dehydrate. Suction may be applied to facilitate moisture removal. The moisture permeability and/or absorbency of the electrode carrying member allows the moisture to leave the ablation site so as to prevent the moisture from providing a path of conductivity for the current.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/084,791, filed May 8, 1998, and is a Continuation in Part ofcopending U.S. application Ser. No. 08/632,516, filed Apr. 12, 1996, nowU.S. Pat. No. 5,769,880, issued Jun. 23, 1998.

FIELD OF THE INVENTION

The present invention relates generally to the field of apparatuses andmethods for ablating or coagulating the interior surfaces of bodyorgans. Specifically, it relates to an apparatus and method for ablatingthe interior linings of body organs such as the uterus and gallbladder.

BACKGROUND OF THE INVENTION

Ablation of the interior lining of a body organ is a procedure whichinvolves heating the organ lining to temperatures which destroy thecells of the lining or coagulate tissue proteins for hemostasis. Such aprocedure may be performed as a treatment to one of many conditions,such as chronic bleeding of the endometrial layer of the uterus orabnormalities of the mucosal layer of the gallbladder. Existing methodsfor effecting ablation include circulation of heated fluid inside theorgan (either directly or inside a balloon), laser treatment of theorgan lining, and resistive heating using application of RF energy tothe tissue to be ablated.

U.S. Pat. No. 5,084,044 describes an apparatus for endometrial ablationin which a bladder is inserted into the uterus. Heated fluid is thencirculated through the balloon to expand the balloon into contact withthe endometrium and to ablate the endometrium thermally. U.S. Pat. No.5,443,470 describes an apparatus for endometrial ablation in which anexpandable bladder is provided with electrodes on its outer surface.After the apparatus is positioned inside the uterus, a non-conductivegas or liquid is used to fill the balloon, causing the balloon to pushthe electrodes into contact with the endometrial surface. RF energy issupplied to the electrodes to ablate the endometrial tissue usingresistive heating.

These ablation devices are satisfactory for carrying out ablationprocedures. However, because no data or feedback is available to guidethe physician as to how deep the tissue ablation has progressed,controlling the ablation depth and ablation profile with such devicescan only be done by assumption.

For example, the heated fluid method is a very passive and ineffectiveheating process which relies on the heat conductivity of the tissue.This process does not account for variations in factors such as theamount of contact between the balloon and the underlying tissue, orcooling effects such as those of blood circulating through the organ. RFablation techniques can achieve more effective ablation since it relieson active heating of the tissue using RF energy, but presently the depthof ablation using RF techniques can only be estimated by the physiciansince no feedback can be provided as to actual ablation depth.

Both the heated fluid techniques and the latest RF techniques must beperformed using great care to prevent over ablation. Monitoring oftissue surface temperature is normally carried out during these ablationprocedures to ensure the temperature does not exceed 100° C. If thetemperature exceeds 100° C., the fluid within the tissue begins to boiland to thereby produce steam. Because ablation is carried out within aclosed cavity within the body, the steam cannot escape and may insteadforce itself deeply into the tissue, or it may pass into areas adjacentto the area intended to be ablated, causing embolism or unintendedburning.

Moreover, in prior art RF devices the water drawn from the tissuecreates a path of conductivity through which current traveling throughthe electrodes will flow. This can prevent the current from travelinginto the tissue to be ablated. Moreover, the presence of this currentpath around the electrodes causes current to be continuously drawn fromthe electrodes. The current heats the liquid drawn from the tissue andthus turns the ablation process into a passive heating method in whichthe heated liquid around the electrodes causes thermal ablation tocontinue well beyond the desired ablation depths.

Another problem with prior art ablation devices is that it is difficultfor a physician to find out when ablation has been carried out to adesired depth within the tissue. Thus, it is often the case that toomuch or too little tissue may be ablated during an ablation procedure.

It is therefore desirable to provide an ablation device which eliminatesthe above-described problem of steam and liquid buildup at the ablationsite. It is further desirable to provide an ablation method and devicewhich allows the depth of ablation to be controlled and whichautomatically discontinues ablation once the desired ablation depth hasbeen reached.

SUMMARY OF THE INVENTION

The present invention is an apparatus and method of ablating and/orcoagulating tissue, such as that of the uterus or other organ. Anablation device is provided which has an electrode array carried by anelongate tubular member. The electrode array includes a fluid permeableelastic member preferably formed of a metallized fabric havinginsulating regions and conductive regions thereon. During use, theelectrode array is positioned in contact with tissue to be ablated,ablation energy is delivered through the array to the tissue to causethe tissue to dehydrate, and moisture generated during dehydration isactively or passively drawn into the array and away from the tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation view of a first embodiment of an ablationdevice according to the present invention, with the handle shown incross-section and with the RF applicator head in a closed condition.

FIG. 2 is a front elevation view of the ablation device of FIG. 1, withthe handle shown in cross-section and with the RF applicator head in anopen condition.

FIG. 3 is a side elevation view of the ablation device of FIG. 2.

FIG. 4 is a top plan view of the ablation device of FIG. 2.

FIG. 5A is a front elevation view of the applicator head and a portionof the main body of the ablation device of FIG. 2, with the main bodyshown in cross-section.

FIG. 5B is a cross-section view of the main body taken along the planedesignated 5B-5B in FIG. 5A.

FIG. 6 is a schematic representation of a uterus showing the ablationdevice of FIG. 1 following insertion of the device into the uterus butprior to retraction of the introducer sheath and activation of thespring members.

FIG. 7 is a schematic representation of a uterus showing the ablationdevice of FIG. 1 following insertion of the device into the uterus andfollowing the retraction of the introducer sheath and the expansion ofthe RF applicator head.

FIG. 8 is a cross-section view of the RF applicator head and the distalportion of the main body of the apparatus of FIG. 1, showing the RFapplicator head in the closed condition.

FIG. 9 is a cross-section view of the RF applicator head and the distalportion of the main body of the apparatus of FIG. 1, showing theconfiguration of RF applicator head after the sheath has been retractedbut before the spring members have been released by proximal movement ofthe shaft.

FIG. 10 is a cross-section view of the RF applicator head and the distalportion of the main body of the apparatus of FIG. 1, showing theconfiguration of RF applicator head after the sheath has been retractedand after the spring members have been released into the fully openedcondition.

FIG. 11 is a cross-section view of a distal portion of an RF ablationdevice similar to FIG. 1 which utilizes an alternative spring memberconfiguration for the RF applicator head.

FIG. 12 is a side elevation view of the distal end of an alternateembodiment of an RF ablation device similar to that of FIG. 1, whichutilizes an RF applicator head having a modified shape.

FIG. 13 is a top plan view of the ablation device of FIG. 12.

FIG. 14 is a representation of a bleeding vessel illustrating use of theablation device of FIG. 12 for general bleeding control.

FIGS. 15 and 16 are representations of a uterus illustrating use of theablation device of FIG. 12 for endometrial ablation.

FIG. 17 is a representation of a prostate gland illustrating use of theablation device of FIG. 12 for prostate ablation.

FIG. 18 is a cross-section view of target tissue for ablation, showingablation electrodes in contact with the tissue surface and illustratingenergy fields generated during bi-polar ablation.

FIGS. 19A-19C are cross-section views of target tissue for ablation,showing electrodes in contact with the tissue surface and illustratinghow varying active electrode density may be used to vary the ablationdepth.

FIG. 20 is a side elevation view, similar to the view of FIG. 2, showingan ablation device according to the present invention in which theelectrode carrying means includes inflatable balloons. For purposes ofclarity, the electrodes on the electrode carrying means are not shown.

FIG. 21 is a side elevation view of a second exemplary embodiment of anablation device according to the present invention, showing the array inthe retracted state.

FIG. 22 is a side elevation view of the ablation device of FIG. 21,showing the array in the deployed state.

FIG. 23 is a top plan view of the applicator head of the apparatus ofFIG. 21.

FIG. 24 is a cross-sectional top view of the encircled region designated24 in FIG. 23.

FIG. 25A is a perspective view of the electrode array of FIG. 23.

FIG. 25B is a distal end view of the applicator head of FIG. 30A.

FIG. 26A is a plan view of a knit that may be used to form theapplicator head.

FIG. 26B is a perspective view of a strand of nylon-wrapped spandex ofthe type that may be used to form the knit of FIG. 26A.

FIGS. 27A, 27B, 27C are top plan views illustrating triangular,parabolic, and rectangular mesh shapes for use as electrode arraysaccording to the present invention.

FIG. 28 is a perspective view showing the flexures and hypotube of thedeflecting mechanism of the applicator head of FIG. 23.

FIG. 29 is a cross-section view of a flexure taken along the planedesignated 29-29 in FIG. 23.

FIG. 30 is a top plan view illustrating the flexure and springarrangement of an alternative configuration of a deflecting mechanismfor an applicator head according to the present invention.

FIG. 31 is a cross-sectional side view of the bobbin portion of theapparatus of FIG. 21.

FIG. 32A is a side elevation view of the handle of the ablation deviceof FIG. 21.

FIG. 32B is a top plan view of the handle of the ablation device of FIG.21. For clarity, portions of the proximal and distal grips are notshown.

FIG. 33 illustrates placement of the applicator head according to thepresent invention in a uterine cavity.

FIG. 34 is a side elevation view of the handle of the ablation apparatusof FIG. 21, showing portions of the apparatus in cross-section.

FIG. 35 is a front elevation view of the upper portion of the proximalhandle grip taken along the plane designated 35-35 in FIG. 32B.

FIGS. 36A, 36B, and 36C are a series of side elevation viewsillustrating the heel member as it becomes engaged with thecorresponding spring member.

FIGS. 37A and 37B are cross-sectional top views of the frame membermounted on the proximal grip section, taken along the plane designated37-37 in FIG. 34 and illustrating one of the load limiting features ofthe second embodiment. FIG. 37A shows the condition of the compressionspring before the heel member moves into abutment with frame member, andFIG. 37B shows the condition of the spring after the heel member movesinto abutment with the frame member.

DETAILED DESCRIPTION

The invention described in this application is an aspect of a larger setof inventions described in the following co-pending applications which ae commonly owned by the assignee of the present invention, and arehereby incorporated by reference: U.S. Provisional Patent ApplicationNo. 60/084,724, filed May 8, 1 998, entitled “APPARATUS AND METHOD FORINTRA-ORGAN MEASUREMENT AND ABLATION” (attorney docket no. ENVS-400);and U.S. Provisional Patent Application No. ______ filed May 8, 1998,entitled “A RADIO-FREQUENCY GENERATOR FOR POWERING AN ABLATION DEVICE”(attorney docket no. ENVS-500).

The ablation apparatus according to the present invention will bedescribed with respect to two exemplary embodiments.

First Exemplary Embodiment—Structure

Referring to FIGS. 1 and 2, an ablation device according to the presentinvention is comprised generally of three major components: RFapplicator head 2, main body 4, and handle 6. Main body 4 includes ashaft 10. The RF applicator head 2 includes an electrode carrying means12 mounted to the distal end of the shaft 10 and an array of electrodes14 formed on the surface of the electrode carrying means 12. An RFgenerator 16 is electrically connected to the electrodes 14 to providemono-polar or bipolar RF energy to them.

Shaft 10 is an elongate member having a hollow interior. Shaft 10 ispreferably 12 inches long and has a preferred cross-sectional diameterof approximately 4 mm. A collar 13 is formed on the exterior of theshaft 10 at the proximal end. As best shown in FIGS. 6 and 7, passivespring member 15 are attached to the distal end of the shaft 10.

Extending through the shaft 10 is a suction/insufflation tube 17 (FIGS.6-9) having a plurality of holes 17 a formed in its distal end. Anarched active spring member 19 is connected between the distal ends ofthe passive spring members 15 and the distal end of thesuction/insufflation tube 17.

Referring to FIG. 2, electrode leads 18 a and 18 b extend through theshaft 10 from distal end 20 to proximal end 22 of the shaft 10. At thedistal end 20 of the shaft 10, each of the leads 18 a, 18 b is coupledto a respective one of the electrodes 14. At the proximal end 22 of theshaft 10, the leads 18 a, 18 b are electrically connected to RFgenerator 16 via an electrical connector 21. During use, the leads 18 a,18 b carry RF energy from the RF generator 16 to the electrodes. Each ofthe leads 18 a, 18 b is insulated and carries energy of an oppositepolarity than the other lead.

Electrically insulated sensor leads 23 a, 23 b (FIGS. 5A and 5B) alsoextend through the shaft 10. Contact sensors 25 a, 25 b are attached tothe distal ends of the sensor leads 23 a, 23 b, respectively and aremounted to the electrode carrying means 12. During use, the sensor leads23 a, 23 b are coupled by the connector 21 to a monitoring module in theRF generator 16 which measures impedance between the sensors 25 a, 25 b.Alternatively, a reference pad may be positioned in contact with thepatient and the impedance between one of the sensors and the referencepad measured.

Referring to FIG. 5B, electrode leads 18 a, 18 b and sensor leads 23 a,23 b extend through the shaft 10 between the external walls of the tube17 and the interior walls of the shaft 10 and they are coupled toelectrical connector 21 which is preferably mounted to the collar 13 onthe shaft 10. Connector 21, which is connectable to the RF generator 16,includes at least four electrical contact rings 21 a-21 d (FIGS. 1 and2) which correspond to each of the leads 18 a, 18 b, 23 a, 23 b. Rings21 a, 21 b receive, from the RF generator, RF energy of positive andnegative polarity, respectively. Rings 21 c, 21 d deliver signals fromthe right and left sensors, respectively, to a monitoring module withinthe RF generator 16.

Referring to FIG. 5A, the electrode carrying means 12 is attached to thedistal end 20 of the shaft 10. A plurality of holes 24 may be formed inthe portion of the distal end 20 of the shaft which lies within theelectrode carrying means 12.

The electrode carrying means 12 preferably has a shape whichapproximates the shape of the body organ which is to be ablated. Forexample, the apparatus shown in FIGS. 1 through 11 has a bicornual shapewhich is desirable for intrauterine ablation. The electrode carryingmeans 12 shown in these figures includes horn regions 26 which duringuse are positioned within the cornual regions of the uterus and whichtherefore extend towards the fallopian tubes.

Electrode carrying means 12 is preferably a sack formed of a materialwhich is non-conductive, which is permeable to moisture and/or which hasa tendency to absorb moisture, and which may be compressed to a smallervolume and subsequently released to its natural size upon elimination ofcompression. Examples of preferred materials for the electrode carryingmeans include open cell sponge, foam, cotton, fabric, or cotton-likematerial, or any other material having the desired characteristics.Alternatively, the electrode carrying means may be formed of ametallized fabric. For convenience, the term “pad” may be usedinterchangeably with the term electrode carrying means to refer to anelectrode carrying means formed of any of the above materials or havingthe listed properties.

Electrodes 14 are preferably attached to the outer surface of theelectrode carrying means 12, such as by deposition or other attachmentmechanism. The electrodes are preferably made of lengths of silver,gold, platinum, or any other conductive material. The electrodes may beattached to the electrode carrying means 12 by electron beam deposition,or they may be formed into coiled wires and bonded to the electrodecarrying member using a flexible adhesive. Naturally, other means ofattaching the electrodes, such as sewing them onto the surface of thecarrying member, may alternatively be used. If the electrode carryingmeans 12 is formed of a metallized fabric, an insulating layer may beetched onto the fabric surface, leaving only the electrode regionsexposed.

The spacing between the electrodes (i.e. the distance between thecenters of adjacent electrodes) and the widths of the electrodes areselected so that ablation will reach predetermined depths within thetissue, particularly when maximum power is delivered through theelectrodes (where maximum power is the level at which low impedance, lowvoltage ablation can be achieved).

The depth of ablation is also effected by the electrode density (i.e.,the percentage of the target tissue area which is in contact with activeelectrode surfaces) and may be regulated by pre-selecting the amount ofthis active electrode coverage. For example, the depth of ablation ismuch greater when the active electrode surface covers more than 10% ofthe target tissue than it is when the active electrode surfaces covers1% of the target tissue.

For example, by using 3-6 mm spacing and an electrode width ofapproximately 0.5-2.5 mm, delivery of approximately 20-40 watts over a9-16 cm² target tissue area will cause ablation to a depth ofapproximately 5-7 millimeters when the active electrode surface coversmore than 10% of the target tissue area. After reaching this ablationdepth, the impedance of the tissue will become so great that ablationwill self-terminate as described with respect to the operation of theinvention.

By contrast, using the same power, spacing, electrode width, and RFfrequency will produce an ablation depth of only 2-3 mm when the activeelectrode surfaces covers less than 1% of the target tissue area. Thiscan be better understood with reference to FIG. 19A, in which highsurface density electrodes are designated 14 a and low surface densityelectrodes are designated 14 b. For purposes of this comparison betweenlow and high surface density electrodes, each bracketed group of lowdensity electrodes is considered to be a single electrode. Thus, theelectrode widths W and spacings S extend as shown in FIG. 19A.

As is apparent from FIG. 19A, the electrodes 14 a, which have moreactive area in contact with the underlying tissue T, produce a region ofablation A1 that extends more deeply into the tissue T than the ablationregion A2 produced by the low density electrodes 14 b, even though theelectrode spacings and widths are the same for the high and low densityelectrodes.

Some examples of electrode widths, having spacings with more than 10%active electrode surface coverage, and their resultant ablation depth,based on an ablation area of 6 cm² and a power of 20-40 watts, are givenon the following table: ELECTRODE WIDTH SPACING APPROX. DEPTH 1 mm 1-2mm 1-3 mm 1-2.5 mm 3-6 mm 5-7 mm 1-4.5 mm 8-10 mm 8-10 mm

Examples of electrode widths, having spacings with less than 1% activeelectrode surface coverage, and their resultant ablation depth, based onan ablation area of 6 cm² and a power of 20-40 watts, are given on thefollowing table: ELECTRODE WIDTH SPACING APPROX. DEPTH 1 mm 1-2 mm 0.5-1mm 1-2.5 mm 3-6 mm 2-3 mm 1-4.5 mm 8-10 mm 2-3 mm

Thus it can be seen that the depth of ablation is significantly lesswhen the active electrode surface coverage is decreased.

In the preferred embodiment, the preferred electrode spacing isapproximately 8-10 mm in the horn regions 26 with the active electrodesurfaces covering approximately 1% of the target region. Approximately1-2 mm electrode spacing (with 10% active electrode coverage) ispreferred in the cervical region (designated 28) and approximately 3-6mm (with greater than 10% active electrode surface coverage) ispreferred in the main body region.

The RF generator 16 may be configured to include a controller whichgives the user a choice of which electrodes should be energized during aparticular application in order to give the user control of ablationdepth. For example, during an application for which deep ablation isdesired, the user may elect to have the generator energize every otherelectrode, to thereby optimize the effective spacing of the electrodesand to decrease the percentage of active electrode surface coverage, aswill be described-below with respect to FIG. 18.

Although the electrodes shown in the drawings are arranged in aparticular pattern, it should be appreciated that the electrodes may bearranged in any pattern to provide ablation to desired depths.

Referring to FIGS. 6 and 7, an introducer sheath 32 facilitatesinsertion of the apparatus into, and removal of the apparatus from, thebody organ to be ablated. The sheath 32 is a tubular member which istelescopically slidable over the shaft 10. The sheath 32 is slidablebetween a distal condition, shown in FIG. 6, in which the electrodecarrying means 12 is compressed inside the sheath, and a proximalcondition in which the sheath 32 is moved proximally to release theelectrode carrying means from inside it (FIG. 7). By compressing theelectrode carrying means 12 to a small volume, the electrode carryingmeans and electrodes can be easily inserted into the body cavity (suchas into the uterus via the vaginal opening).

A handle 34 attached to the sheath 32 provides finger holds to allow formanipulation of the sheath 32. Handle 34 is slidably mounted on a handlerail 35 which includes a sleeve 33, a finger cutout 37, and a pair ofspaced rails 35 a, 35 b extending between the sleeve 33 and the fingercutout 37. The shaft 10 and sheath 32 slidably extend through the sleeve33 and between the rails 35 a, 35 b. The tube 17 also extends throughthe sleeve 33 and between the rails 35 a, 35 b, and its proximal end isfixed to the handle rail 35 near the finger cutout 37.

A compression spring 39 is disposed around the proximal most portion ofthe suction/insufflation tube 17 which lies between the rails 35 a, 35b. One end of the compression spring 39 rests against the collar 13 onthe shaft 10, while the opposite end of the compression spring restsagainst the handle rail 35. During use, the sheath 32 is retracted fromthe electrode carrying means 12 by squeezing the handle 34 towards thefinger cutout 37 to slide the sheath 32 in the distal direction. Whenthe handle 34 advances against the collar 13, the shaft 10 (which isattached to the collar 13) is forced to slide in the proximal direction,causing compression of the spring 39 against the handle rail 35. Themovement of the shaft 10 relative to the suction/insufflation tube 17causes the shaft 10 to pull proximally on the passive spring member 15.Proximal movement of the passive spring member 15 in turn pulls againstthe active spring member 19, causing it to move to the opened conditionshown in FIG. 7. Unless the shaft is held in this retracted condition,the compression spring 39 will push the collar and thus the shaftdistally, forcing the RF applicator head to close. A locking mechanism(not shown) may be provided to hold the shaft in the fully withdrawncondition to prevent inadvertent closure of the spring members duringthe ablation procedure.

The amount by which the springs 15, 19 are spread may be controlled bymanipulating the handle 34 to slide the shaft 10 (via collar 13),proximally or distally. Such sliding movement of the shaft 10 causesforceps-like movement of the spring members 15, 19.

A flow pathway 36 is formed in the handle rail 35 and is fluidly coupledto a suction/insufflation port 38. The proximal end of thesuction/insufflation tube 17 is fluidly coupled to the flow pathway sothat gas fluid may be introduced into, or withdrawn from thesuction/insufflation tube 17 via the suction/insufflation port 38. Forexample, suction may be applied to the fluid port 38 using asuction/insufflation unit 40. This causes water vapor within the uterinecavity to pass through the permeable electrode carrying means 12, intothe suction/insufflation tube 17 via holes 17 a, through the tube 17,and through the suction/insufflation unit 40 via the port 38. Ifinsufflation of the uterine cavity is desired, insufflation gas, such ascarbon dioxide, may be introduced into the suction/insufflation tube 17via the port 38. The insufflation gas travels through the tube 17,through the holes 17 a, and into the uterine cavity through thepermeable electrode carrying member 12.

If desirable, additional components may be provided for endoscopicvisualization purposes. For example, lumen 42, 44, and 46 may be formedin the walls of the introducer sheath 32 as shown in FIG. 5B. An imagingconduit, such as a fiberoptic cable 48, extends through lumen 42 and iscoupled via a camera cable 43 to a camera 45. Images taken from thecamera may be displayed on a monitor 56. An illumination fiber 50extends through lumen 44 and is coupled to an illumination source 54.The third lumen 46 is an instrument channel through which surgicalinstruments may be introduced into the uterine cavity, if necessary.

Because during use it is most desirable for the electrodes 14 on thesurface of the electrode carrying means 12 to be held in contact withthe interior surface of the organ to be ablated, the electrode carryingmeans 12 may be provide to have additional components inside it that addstructural integrity to the electrode carrying means when it is deployedwithin the body.

For example, referring to FIG. 11, alternative spring members 15 a, 19 amay be attached to the shaft 10 and biased such that, when in a restingstate, the spring members are positioned in the fully resting conditionshown in FIG. 11. Such spring members would spring to the restingcondition upon withdrawal of the sheath 32 from the RF applicator head2.

Alternatively, a pair of inflatable balloons 52 may be arranged insidethe electrode carrying means 12 as shown in FIG. 20 and connected to atube (not shown) extending through the shaft 10 and into the balloons52. After insertion of the apparatus into the organ and followingretraction of the sheath 32, the balloons 52 would be inflated byintroduction of an inflation medium such as air into the balloons via aport similar to port 38 using an apparatus similar to thesuction/insufflation apparatus 40.

Structural integrity may also be added to the electrode carrying meansthrough the application of suction to the proximal end 22 of thesuction/insufflation tube 17. Application of suction using thesuction/insufflation device 40 would draw the organ tissue towards theelectrode carrying means 12 and thus into better contact with theelectrodes 14.

FIGS. 12 and 13 show an alternative embodiment of an ablation deviceaccording to the present invention. In the alternative embodiment, anelectrode carrying means 12 a is provided which has a shape which isgenerally tubular and thus is not specific to any particular organshape. An ablation device having a general shape such as this may beused anywhere within the body where ablation or coagulation is needed.For example, the alternative embodiment is useful for bleeding controlduring laparoscopic surgery (FIG. 14), tissue ablation in the prostategland (FIG. 17), and also intrauterine ablation (FIGS. 15 and 16).

First Exemplary Embodiment—Operation

Operation of the first exemplary embodiment of an ablation deviceaccording to the present invention will next be described.

Referring to FIG. 1, the device is initially configured for use bypositioning the introducer sheath 32 distally along the shaft 10, suchthat it compresses the electrode carrying means 12 within its walls.

At this time, the electrical connector 21 is connected to the RFgenerator 16, and the fiberoptic cable 48 and the illumination cable 50are connected to the illumination source, monitor, and camera, 54, 56,45. The suction/insufflation unit 40 is attached to suction/insufflationport 38 on the handle rail 35. The suction/insufflation unit 40 ispreferably set to deliver carbon dioxide at an insufflation pressure of20-200 mmHg.

Next, the distal end of the apparatus is inserted through the vaginalopening V and into the uterus U as shown in FIG. 6, until the distal endof the introducer sheath 32 contacts the fundus F of the uterus. At thispoint, carbon dioxide gas is introduced into the tube 17 via the port38, and it enters the uterine cavity, thereby expanding the uterinecavity from a flat triangular shape to a 1-2 cm high triangular cavity.The physician may observe (using the camera 45 and monitor 56) theinternal cavities using images detected by a fiberoptic cable 48inserted through lumen 42. If, upon observation, the physiciandetermines that a tissue biopsy or other procedure is needed, therequired instruments may be inserted into the uterine cavity via theinstrument channel 46.

Following insertion, the handle 34 is withdrawn until it abuts thecollar 13. At this point, the sheath 32 exposes the electrode carryingmember 12 but the electrode carrying member 12 is not yet fully expanded(see FIG. 9), because the spring members 15, 19 have not yet been movedto their open condition. The handle 34 is withdrawn further, causing theshaft 10 to move proximally relative to the suction/insufflation tube17, causing the passive spring members 15 to pull tile active springmembers 19, causing them to open into the opened condition shown FIG.10.

The physician may confirm proper positioning of the electrode carryingmember 12 using the monitor 56, which displays images from thefiberoptic cable 48.

Proper positioning of the device and sufficient contact between theelectrode carrying member 12 and the endometrium may further beconfirmed using the contact sensors 25 a, 25 b. The monitoring module ofthe RF generator measures the impedance between these sensors usingconventional means. If there is good contact between the sensors and theendometrium, the measured impedance will be approximately 20-180 ohm,depending on the water content of the endometrial lining.

The sensors are positioned on the distal portions of the bicornualshaped electrode carrying member 12, which during use are positioned inthe regions within the uterus in which it is most difficult to achievegood contact with the endometrium. Thus, an indication from the sensors25 a, 25 b that there is sound contact between the sensors and theendometrial surface indicates that good electrode contact has been madewith the endometrium.

Next, insufflation is terminated. Approximately 1-5 cc of saline may beintroduced via suction/insufflation tube 17 to initially wet theelectrodes and to improve electrode electrical contact with the tissue.After introduction of saline, the suction/insufflation device 40 isswitched to a suctioning mode. As described above, the application ofsuction to the RF applicator head 2 via the suction/insufflation tube 17collapses the uterine cavity onto the RF applicator head 2 and thusassures better contact between the electrodes and the endometrialtissue.

If the generally tubular apparatus of FIGS. 12 and 13 is used, thedevice is angled into contact with one side of the uterus during theablation procedure. Once ablation is completed, the device (or a newdevice) is repositioned in contact with the opposite side and theprocedure is repeated. See. FIGS. 15 and 16.

Next, RF energy at preferably about 500 kHz and at a constant power ofapproximately 30 W is applied to the electrodes. As shown in FIG. 5 a,it is preferable that each electrode be energized at a polarity oppositefrom that of its neighboring electrodes. By doing so, energy fieldpatterns, designated F1, F2 and F4 in FIG. 18, are generated between theelectrode sites and thus help to direct the flow of current through thetissue T to form a region of ablation A. As can be seen in FIG. 18, ifelectrode spacing is increased such by energizing, for example everythird or fifth electrode rather than all electrodes, the energy patternswill extend more deeply into the tissue. (See, for example, pattern F2which results from energization of electrodes having a non-energizedelectrode between them, or pattern F4 which results from energization ofelectrodes having two non-energized electrodes between them).

Moreover, ablation depth may be controlled as described above byproviding low surface density electrodes on areas of the electrodecarrying member which will contact tissue areas at which a smallerablation depth is required (see FIG. 19A). Referring to FIG. 19B, ifmultiple, closely spaced, electrodes 14 are provided on the electrodecarrying member, a user may set the RF generator to energize electrodeswhich will produce a desired electrode spacing and active electrodearea. For example, alternate electrodes may be energized as shown inFIG. 19B, with the first three energized electrodes having positivepolarity, the second three having negative polarity, etc.

As another example, shown in FIG. 19C, if greater ablation depth isdesired the first five electrodes may be positively energized, and theseventh through eleventh electrodes negatively energized, with the sixthelectrode remaining inactivated to provide adequate electrode spacing.

As the endometrial tissue heats, moisture begins to be released from thetissue. The moisture permeates the electrode carrying member 12 and isthereby drawn away from the electrodes. The moisture may pass throughthe holes 17 a in the suction/insufflation tube 17 and leave thesuction/insufflation tube 17 at its proximal end via port 38 as shown inFIG. 7. Moisture removal from the ablation site may be furtherfacilitated by the application of suction to the shaft 10 using thesuction/insufflation unit 40.

Removal of the moisture from the ablation site prevents formation of aliquid layer around the electrodes. As described above, liquid build-upat the ablation site is detrimental in that provides a conductive layerthat carries current from the electrodes even when ablation has reachedthe desired depth. This continued current flow heats the liquid andsurrounding tissue, and thus causes ablation to continue byunpredictable thermal conduction means.

Tissue which has been ablated becomes dehydrated and thus decreases inconductivity. By shunting moisture away from the ablation site and thuspreventing liquid build-up, there is no liquid conductor at the ablationarea during use of the ablation device of the present invention. Thus,when ablation has reached the desired depth, the impedance at the tissuesurface becomes sufficiently high to stop or nearly stop the flow ofcurrent into the tissue. RF ablation thereby stops and thermal ablationdoes not occur in significant amounts. If the RF generator is equippedwith an impedance monitor, a physician utilizing the ablation device canmonitor the impedance at the electrodes and will know that ablation hasself-terminated once the impedance rises to a certain level and thenremains fairly constant. By contrast, if a prior art bipolar RF ablationdevice was used together with an impedance monitor, the presence ofliquid around the electrodes would cause the impedance monitor to give alow impedance reading regardless of the depth of ablation which hadalready been carried out, since current would continue to travel throughthe low-impedance liquid layer.

Other means for monitoring and terminating ablation may also beprovided. For example, a thermocouple or other temperature sensor may beinserted to a predetermined depth in the tissue to monitor thetemperature of the tissue and terminate the delivery of RF energy orotherwise signal the user when the tissue has reached a desired ablationtemperature.

Once the process has self terminated, 1-5 cc of saline can be introducedvia suction/insufflation tube 17 and allowed to sit for a short time toaid separation of the electrode from the tissue surface. The suctioninsufflation device 40 is then switched to provide insufflation ofcarbon dioxide at a pressure of 20-200 mmHg. The insufflation pressurehelps to lift the ablated tissue away from the RF applicator head 2 andto thus ease the closing of the RF applicator head. The RF applicatorhead 2 is moved to the closed position by sliding the handle 34 in adistal direction to fold the spring members 15, 19 along the axis of thedevice and to cause the introducer sheath 32 to slide over the folded RFapplicator head. The physician may visually confirm the sufficiency ofthe ablation using the monitor 56. Finally, the apparatus is removedfrom the uterine cavity.

Second Exemplary Embodiment—Structure

A second embodiment of an ablation device 100 in accordance with thepresent invention is shown in FIGS. 21-37B. The second embodimentdiffers from the first embodiment primarily in its electrode pattern andin the mechanism used to deploy the electrode applicator head or array.Naturally, aspects of the first and second exemplary embodiments andtheir methods of operation may be combined without departing from thescope of the present invention.

Referring to FIGS. 21 and 22, the second embodiment includes an RFapplicator head 102, a sheath 104, and a handle 106. As with the firstembodiment, the applicator head 102 is slidably disposed within thesheath 104 (FIG. 21) during insertion of the device into the uterinecavity, and the handle 106 is subsequently manipulated to cause theapplicator head 102 to extend from the distal end of the sheath 104(FIG. 22) and to expand into contact with body tissue (FIG. 33).

RF Applicator Head

Referring to FIG. 23, in which the sheath 104 is not shown for clarity,applicator head 102 extends from the distal end of a length of tubing108 which is slidably disposed within the sheath 104. Applicator head102 includes an external electrode array 102 a and an internaldeflecting mechanism 102 b used to expand and tension the array forpositioning into contact with the tissue.

Referring to FIGS. 25A and 25B, the array 102 a of applicator head 102is formed of a stretchable metallized fabric mesh which is preferablyknitted from a nylon and spandex knit plated with gold or otherconductive material. In one array design, the knit (shown in FIGS. 26Aand 26B) is formed of three monofilaments of nylon 109 a knittedtogether with single yarns of spandex 109 b. Each yarn of spandex 109 bhas a double helix 109 c of five nylon monofilaments coiled around it.

This knit of elastic (spandex) and inelastic (nylon) yarns is beneficialfor a number of reasons. For example, knitting elastic and relativelyinelastic yarns allows the overall deformability of the array to bepre-selected.

The mesh is preferably constructed so as to have greater elasticity inthe transverse direction (T) than in the longitudinal direction (L). Ina preferred mesh design, the transverse elasticity is on the order ofapproximately 300% whereas the longitudinal elasticity is on the orderof approximately 100%. The large transverse elasticity of the arrayallows it to be used in a wide range of uterine sizes.

Another advantage provided by the combination of elastic and relativelyinelastic yarns is that the elastic yarns provide the needed elasticityto the array while the relatively inelastic yarns provide relativelynon-stretchable members to which the metallization can adhere withoutcracking during expansion of the array. In the knit configurationdescribed above, the metallization adheres to the nylon coiled aroundthe spandex. During expansion of the array, the spandex elongates andthe nylon double helix at least partially elongates from-its coiledconfiguration.

One process which may be used to apply the gold to the nylon/spandexknit involves plating the knit with silver using known processes whichinvolve application of other materials as base layers prior toapplication of the silver to ensure that the silver will adhere. Next,the insulating regions 110 (described below) are etched onto the silver,and afterwards the gold is plated onto the silver. Gold is desirable forthe array because of it has a relatively smooth surface, is a very inertmaterial, and has sufficient ductility that it will not crack as thenylon coil elongates during use.

The mesh may be configured in a variety of shapes, including but notlimited to the triangular shape S1, parabolic S2, and rectangular S3shapes shown in FIGS. 27A, 27B and 27C, respectively.

Turning again to FIGS. 25A and 25B, when in its expanded state, thearray 102 a includes a pair of broad faces 1 12 spaced apart from oneanother. Narrower side faces 114 extend between the broad faces 112along the sides of the applicator head 102, and a distal face 116extends between the broad faces 112 at the distal end of the applicatorhead 102.

Insulating regions 110 are formed on the applicator head to divide themesh into electrode regions. The insulated regions 110 are preferablyformed using etching techniques to remove the conductive metal from themesh, although alternate methods may also be used, such as by knittingconductive and non-conductive materials together to form the array.

The array may be divided by the insulated regions 110 into a variety ofelectrode configurations. In a preferred configuration the insulatingregions 110 divide the applicator head into four electrodes 118 a-118 dby creating two electrodes on each of the broad faces 112. To createthis four-electrode pattern, insulating regions 110 are placedlongitudinally along each of the broad faces 112 as well as along thelength of each of the faces 114, 116. The electrodes 118 a-118 d areused for ablation and, if desired, to measure tissue impedance duringuse.

Deflecting mechanism 102 b and its deployment structure is enclosedwithin electrode array 102 a. Referring to FIG. 23, external hypotube120 extends from tubing 108 and an internal hypotube 122 is slidably andco-axially disposed within hypotube 120. Flexures 124 extend from thetubing 108 on opposite sides of external hypotube 120. A plurality oflongitudinally spaced apertures 126 (FIG. 28) are formed in each flexure124. During use, apertures 126 allow moisture to pass through theflexures and to be drawn into exposed distal end of hypotube 120 using avacuum source fluidly coupled to hypotube 120.

Each flexure 124 preferably includes conductive regions that areelectrically coupled to the array 102 a for delivery of RF energy to thebody tissue. Referring to FIG. 29, strips 128 of copper tape or otherconductive material extend along opposite surfaces of each flexure 124.Each strip 128 is electrically insulated from the other strip 128 by anon-conductive coating on the flexure. Conductor leads (not shown) areelectrically coupled to the strips 128 and extend through tubing 108(FIG. 23) to an electrical cord 130 (FIG. 21) which is attachable to theRF generator.

During use, one strip 128 on each conductor is electrically coupled viathe conductor leads to one terminal on the RF generator while the otherstrip is electrically coupled to the opposite terminal, thus causing thearray on the applicator head to have regions of alternating positive andnegative polarity.

The flexures may alternatively be formed using a conductive material ora conductively coated material having insulating regions formed thereonto divide the flexure surfaces into multiple conductive regions.Moreover, alternative methods such as electrode leads independent of theflexures 124 may instead be used for electrically connecting theelectrode array to the source of RF energy.

It is important to ensure proper alignment between the conductiveregions of the flexures 124 (e.g. copper strips 128) and the electrodes118 a-118 d in order to maintain electrical contact between the two.Strands of thread 134 (which may be nylon) (FIG. 23) are preferably sewnthrough the array 102 a and around the flexures 124 in order to preventthe conductive regions 128 from slipping out of alignment with theelectrodes 118 a-118 d. Alternate methods for maintaining contactbetween the array 102 a and the conductive regions 128 include usingtiny bendable barbs extending between the flexures 124 and the array 102a to hook the array to the conductive regions 128, or bonding the arrayto the flexures using an adhesive applied along the insulating regionsof the flexures.

Referring again to FIG. 23, internal flexures 136 extend laterally andlongitudinally from the exterior surface of hypotube 122. Each internalflexure 136 is connected at its distal end to one of the flexures 124and a transverse ribbon 138 extends between the distal portions of theinternal flexures 136. Transverse ribbon 138 is preferably pre-shapedsuch that when in the relaxed condition the ribbon assumes thecorrugated configuration shown in FIG. 23 and such that when in acompressed condition it is folded along the plurality of creases 140that extend along its length. Flexures 124, 136 and ribbon 138 arepreferably an insulated spring material such as heat treated 17-7 PHstainless steel.

The deflecting mechanism is preferably configured such that the distaltips of the flexures 124 are sufficiently flexible to prevent tissuepuncture during deployment and/or use. Such an atraumatic tip design maybe carried out in a number of ways, such as by manufacturing the distalsections 124 a (FIG. 28) of the flexures from a material that is moreflexible than the proximal sections 124 b. For example, flexures 124 maybe provided to have proximal sections formed of a material having amodulus of approximately 28×10⁶ psi and distal sections having adurometer of approximately 72 D.

Alternatively, referring to FIG. 30, the flexures 124 may be joined tothe internal flexures 136 at a location more proximal than the distaltips of the flexures 124, allowing them to move more freely and to adaptto the contour of the surface against which they are positioned (seedashed lines in FIG. 30). Given that uterine sizes and shapes varywidely between women, the atraumatic tip design is further beneficial inthat it allows the device to more accurately conform to the shape of theuterus in which it is deployed while minimizing the chance of injury.

The deflecting mechanism formed by the flexures 124, 136, and ribbon 138forms the array into the substantially triangular shape shown in FIG.23, which is particularly adaptable to most uterine shapes. As set forthin detail below, during use distal and proximal grips 142, 144 forminghandle 106 are squeezed towards one another to withdraw the sheath anddeploy the applicator head. This action results in relative rearwardmotion of the hypotube 120 and relative forward motion of the hypotube122. The relative motion between the hypotubes causes deflection inflexures 124, 136 which deploys and tensions the electrode array 102 a.

Measurement Device

The ablation device according to the second embodiment includes ameasurement device for easily measuring the uterine width and fordisplaying the measured width on a gauge 146 (FIG. 21). The measurementdevice utilizes non-conductive (e.g. nylon) suturing threads 148 thatextend from the hypotube 122 and that have distal ends attached to thedistal portion of the deflecting mechanism (FIG. 23). As shown in FIG.24, threads 148 are preferably formed of a single strand 150 threadedthrough a wire loop 152 and folded over on itself. Wire loop 152 formsthe distal end of an elongate wire 154 which may be formed of stainlesssteel or other wire.

Referring to FIG. 31, wire 154 extends through the hypotube 122 and issecured to a rotatable bobbin 156. The rotatable bobbin 156 includes adial face 158 preferably covered in a clear plastic. As can be seen inFIG. 32, dial face 158 includes calibration markings corresponding to anappropriate range of uterine widths. The bobbin is disposed within agauge housing 160 and a corresponding marker line 162 is printed on thegauge housing. A torsion spring 1 64 provides rotational resistance tothe bobbin 156.

Expansion of the applicator head 102 during use pulls threads 148 (FIG.23) and thus wire 154 (FIG. 24) in a distal direction. Wire 154 pullsagainst the bobbin 156 (FIG. 31), causing it to rotate. Rotation of thebobbin positions one of the calibration markings on dial face 158 intoalignment with the marker line 162 (FIG. 32B) to indicate the distancebetween the distal tips of flexures 124 and thus the uterine width.

The uterine width and length (as determined using a conventional soundor other means) are preferably input into an RF generator system andused by the system to calculate an appropriate ablation power as will bedescribed below. Alternately, the width as measured by the apparatus ofthe invention and length as measured by other means may be used by theuser to calculate the power to be supplied to the array to achieve thedesired ablation depth.

The uterine width may alternatively be measured using other means,including by using a strain gauge in combination with an A/D converterto transduce the separation distance of the flexures 124 and toelectronically transmit the uterine width to the RF generator.

Control of Ablation Depth

The most optimal electrocoagulation occurs when relatively deep ablationis carried out in the regions of the uterus at which the endometrium isthickest, and when relatively shallower ablation is carried out in areasin which the endometrium is shallower. A desirable range of ablationdepths includes approximately 2-3 mm for the cervical os and the cornualregions, and approximately 7-8 mm in the main body of the uterus wherethe endometrium is substantially thicker.

As discussed with respect to the first embodiment, a number of factorsinfluence the ablation depth that can be achieved using a given powerapplied to a bipolar electrode array. These include the power suppliedby the RF generator, the distance between the centers of adjacentelectrodes (“center-to-center distance”), the electrode density (i.e.,the porosity of the array fabric or the percent of the array surfacethat is metallic), the edge gap (i.e. the distance between the edges ofadjacent electrode poles), and the electrode surface area. Other factorsinclude blood flow (which in slower-ablating systems can dissipate theRF) and the impedance limit.

Certain of these factors may be utilized in the present invention tocontrol ablation depth and to provide deeper ablation at areas requiringdeeper ablation and to provide shallower regions in areas where deepablation is not needed. For example, as center-to-center distanceincreases, the depth of ablation increases until a point where thecenter to center distance is so great that the strength of the RF fieldis too diffuse to excite the tissue. It can been seen with reference toFIG. 33 that the center to center distance d1 between the electrodes 118a, 118 b is larger within the region of the array that lies in the mainbody of the uterus and thus contributes to deeper ablation. The centerto center distance d2 between electrodes 118 a, 118 b is smaller towardsthe cervical canal where it contributes to shallower ablation. At thedistal end of the device, the shorter center to center distances d3extend between top and bottom electrodes 118 b, 118 c and 118 a, 118 dand again contribute to shallower ablation.

Naturally, because the array 102 a expands to accommodate the size ofthe uterus in which it is deployed, the dimensions of the array 102 avary. One embodiment of the array 102 a includes a range of widths of atleast approximately 2.5-4.5 cm, a range of lengths of at leastapproximately 4-6 cm, and a density of approximately 35%-45%.

The power supplied to the array by the RF generator is calculated by theRF generator system to accommodate the electrode area required for aparticular patient. As discussed above, the uterine width is measured bythe applicator head 102 and displayed on gauge 146. The uterine lengthis measured using a sound, which is an instrument conventionally usedfor that purpose. It should be noted that calibration markings of thetype used on a conventional sound device, or other structure for lengthmeasurement, may be included on the present invention to allow it to beused for length measurement as well.

The user enters the measured dimensions into the RF generator systemusing an input device, and the RF generator system calculates or obtainsthe appropriate set power from a stored look-up table using the uterinewidth and length as entered by the user. An EPROM within the RFgenerator system converts the length and width to a set power levelaccording to the following relationship:P=L×W×5.5Where P is the power level in watts, L is the length in centimeters, Wis the width in centimeters, and 5.5 is a constant having units of wattsper square centimeter.

Alternatively, the user may manually calculate the power setting fromthe length and width, or s/he may be provided with a table of suggestedpower settings for various electrode areas (as determined by themeasured length and width) and will manually set the power on the RFgenerator accordingly.

Handle

Referring again to FIGS. 21 and 22, the handle 106 of the RF ablationdevice according to the second embodiment includes a distal grip section142 and a proximal grip section 144 that are pivotally attached to oneanother at pivot pin 166.

The proximal grip section 144 is coupled to the hypotube 122 (FIG. 23)via yoke 168, overload spring 170 and spring stop 172, each of which isshown in the section view of FIG. 34. The distal grip section 142 iscoupled to the external hypotube 120 via male and female couplers 174,176 (see FIGS. 32A and 32B). Squeezing the grip sections 142, 144towards one another thus causes relative movement between the externalhypotube 120 and the internal hypotube 122. This relative slidingmovement results in deployment of the deflecting mechanism 102 b fromthe distal end of the sheath and expansion of the array 102 a to itsexpanded state.

Referring to FIGS. 32A and B, rack 180 is formed on male coupler 174 andcalibration markings 182 are printed adjacent the rack 180. Thecalibration markings 182 correspond to a variety of uterine lengths andmay include lengths ranging from, for example, 4.0 to 6.0 cm in 0.5 cmincrements.

A sliding collar 184 is slidably disposed on the tubing 108 and isslidable over male coupler 174. Sliding collar 184 includes a rotatingcollar 186 and a female coupler 176 that includes a wedge-shaped heel188. A locking spring member 190 (FIGS. 32B and 35) extends across anaperture 192 formed in the proximal grip 144 in alignment with the heel188. When the distal and proximal handle sections are squeezed togetherto deploy the array, the heel 188 passes into the aperture 192. Itsinclined lower surface gradually depresses the spring member 190 as theheel moves further into the aperture 192. See FIGS. 36A and 36B. Afterpassing completely over the spring member, the heel moves out of contactwith the spring member. The spring member snaps upwardly therebyengaging the heel in the locked position. See FIG. 36C.

A release lever 194 (FIG. 35) is attached to the free end of the springmember 190. To disengage the spring lock, release lever 194 is depressedto lower spring member 190 so that the inclined heel can pass over thespring member and thus out of the aperture 192.

Referring again to FIGS. 32A and 32B, sliding collar 184 is configuredto allow the user to limit longitudinal extension of the array 102 a toa distance commensurate with a patient's predetermined uterine length.It does so by allowing the user to adjust the relative longitudinalposition of male coupler 174 relative to the female coupler 176 usingthe rotating collar 186 to lock and unlock the female coupler from therack 180 and the male coupler 174. Locking the female coupler to therack 180 and male coupler 174 will limit extension of the array toapproximately the predetermined uterine length, as shown on thecalibration markings 182.

Once the uterine length has been measured using a conventional sound,the user positions sliding collar 184 adjacent to calibration marks 182corresponding to the measured uterine length (e.g. 4.5 cm). Afterwards,the user rotates the collar section 186 to engage its internallypositioned teeth with the rack 180. This locks the longitudinal positionof the heel 188 such that it will engage with the spring member 190 onthe proximal grip when the array has been exposed to the length set bythe sliding collar.

The handle 106 includes a pair of spring assemblies which facilitatecontrolled deployment and stowage of the array 102 a. One of the springassemblies controls movement of the grips 142, 144 to automatically stowthe array 102 a into the sheath 104 when the user stops squeezing thegrips 142, 144 towards one another. The other of the spring assembliescontrols the transverse movement of the spring flexures 124 to theexpanded condition by limiting the maximum load that can be applied tothe deployment mechanism 102 b.

FIG. 34 shows the distal and proximal grips 142 and 144 in partialcross-section. The first spring assembly for controlled stowage includesa handle return mandrel 196 that is slidably disposed within theproximal grip 144. A compression spring 198 surrounds a portion of thereturn mandrel 196, and a retaining ring 200 is attached to the mandrel196 above the spring 198. A spring stop 202 is disposed between thespring 198 and the retaining ring.

The lowermost end of the return mandrel 196 is pivotally engaged by acoupling member 204 on distal grip 142. Relative movement of the grips142, 144 towards one another causes the coupling member 204 to pull thereturn member downwardly with the proximal grip 144 as indicated byarrows. Downward movement of the mandrel 196 causes its retaining ring200 and spring stop 202 to bear downwardly against the compressionspring 198, thereby providing a movement which acts to rotate the grips142, 144 away from one another. When tension against the grips 142, 144is released (assuming that heel 188 is not locked into engagement withspring member 190) the grips rotate apart into the opened position asthe compression spring 198 returns to the initial state, stowing theapplicator head inside the sheath.

The second spring assembly for controlling array deployment is designedto control separation of the flexures. It includes a frame member 178disposed over yoke 168, which is pivotally attached to proximal grip144. Tubing 108 extends from the array 102 a (see FIG. 23), through thesheath 104 and is fixed at its proximal end to the frame member 178.Hypotube 122 does not terminate at this point but instead extends beyondthe proximal end of tubing 108 and through a window 206 in the framemember. Its proximal end 208 is slidably located within frame member 178proximally of the window 206 and is fluidly coupled to a vacuum port 210by fluid channel 212. Hypotube 120 terminates within the frame. Itsproximal end is fixed within the distal end of the frame.

A spring stop 214 is fixed to a section of the hypotube within thewindow 206, and a compression spring 170 is disposed around the hypotubebetween the spring stop 172 and yoke 168. See FIGS. 32B and 34.

When the distal and proximal grips are moved towards one another, therelative rearward motion of the distal grip causes the distal grip towithdraw the sheath 104 from the array 102 a. Referring to FIGS. 37A and37B, this motion continues until female coupler 176 contacts and bearsagainst frame member 178. Continued motion between the grips causes arelative rearward motion in the frame which causes the same rearwardrelative motion in external hypotube 120. An opposing force is developedin yoke 168, which causes a relative forward motion in hypotube 122. Therelative motion between the hypotubes causes deflection in flexures 124,136 which deflect in a manner that deploys and tensions the electrodearray. Compression spring 170 acts to limit the force developed by theoperator against hypotubes 120, 122, thus limiting the force of flexures124, 136 acting on the array and the target tissue surrounding thearray.

Referring to FIG. 21, collar 214 is slidably mounted on sheath 104.Before the device is inserted into the uterus, collar 214 can bepositioned along sheath 104 to the position measured by-the uterinesound. Once in position, the collar provides visual and tactile feedbackto the user to assure the device has been inserted the proper distance.In addition, after the applicator head 102 has been deployed, if thepatient's cervical canal diameter is larger than the sheath dimensions,the collar 214 can be moved distally towards the cervix, making contactwith it and creating a pneumatic seal between the sheath and cervix.

Second Exemplary Embodiment—Operation

In preparation for ablating the uterus utilizing the second exemplaryembodiment, the user measures the uterine length using a uterine sounddevice. The user next positions sliding collar 184 (FIG. 32B) adjacentto calibration marks 182 corresponding to the measured uterine length(e.g. 4.5 cm) and rotates the collar section 186 to engage itsinternally positioned teeth with the rack 180. This locks thelongitudinal position of the heel 188 (FIG. 32A) such that it willengage with the spring member 190 when the array has been exposed to thelength set by the sliding collar.

Next, with the grips 142, 144 in their resting positions to keep theapplicator head 102 covered by sheath 104, the distal end of the device100 is inserted into the uterus. Once the distal end of the sheath 104is within the uterus, grips 142, 144 are squeezed together to deploy theapplicator head 102 from sheath 104. Grips 142, 144 are squeezed untilheel 188 engages with locking spring member 190 as described withrespect to FIGS. 36A through 36C.

At this point, deflecting mechanism 102 b has deployed the array 102 ainto contact with the uterine walls. The user reads the uterine width,which as described above is transduced from the separation of the springflexures, from gauge 146. The measured length and width are entered intothe RF generator system 250 (FIG. 21) and used to calculate the ablationpower.

Vacuum source 252 (FIG. 21) is activated, causing application of suctionto hypotube 122 via suction port 210. Suction helps to draw uterinetissue into contact with the array 102.

Ablation power is supplied to the electrode array 102 a by the RFgenerator system 250. The tissue is heated as the RF energy passes fromelectrodes 118 a-d to the tissue, causing moisture to be released fromthe tissue. The vacuum source helps to draw moisture from the uterinecavity into the hypotube 122. Moisture withdrawal is facilitated by theapertures 121 formed in flexures 124 by preventing moisture from beingtrapped between the flexures 124 and the lateral walls of the uterus.

If the RF generator 250 includes an impedance monitoring module,impedance may be monitored at the electrodes 118 a-d and the generatormay be programmed to terminate RF delivery automatically once theimpedance rises to a certain level. The generator system may also oralternatively display the measured impedance and allow the user toterminate RF delivery when desired.

When RF delivery is terminated, the user depresses release lever 194 todisengage heel 188 from locking spring member 190 and to thereby allowgrips 142, 144 to move to their expanded (resting condition). Release ofgrips 142, 144 causes applicator head 102 to retract to its unexpandedcondition and further causes applicator head 102 to be withdrawn intothe sheath 104. Finally, the distal end of the device 100 is withdrawnfrom the uterus.

Two embodiments of ablation devices in accordance with the presentinvention have been described herein. These embodiments have been shownfor illustrative purposes only. It should be understood, however, thatthe invention is not intended to be limited to the specifics of theillustrated embodiments but is defined only in terms of the followingclaims.

1-31. (canceled)
 32. A method of treating tissue in a uterus, comprisingthe steps of: providing a moisture permeable electrode member comprisingan array of electrodes; positioning at least a portion of the array ofelectrodes in contact with tissue in a region of a tubal ostium of afallopian tube; delivering RF energy to the electrodes, causing thetissue to release liquid; and applying suction through the moisturepermeable electrode member to draw released liquid from the uterus, thesuction substantially preventing formation of a low-impedance liquidlayer around the electrodes.
 33. The method of claim 32, wherein theapplying step biases the tissue into contact with the array.
 34. Themethod of claim 32, wherein the suction substantially prevents thereleased moisture from creating a layer of liquid which can provide anelectrically conductive pathway between electrodes in the array.
 35. Themethod of claim 32, wherein the positioning step includes passing thearray through the cervical opening in the uterus.
 36. The method ofclaim 32, wherein the electrode array is a mesh electrode array.
 37. Themethod of claim 36, wherein the mesh electrode array comprises a knit ofmetallized yarns.
 38. The method of claim 32, wherein the array isexpandable from a collapsed position to an expanded position and whereinthe positioning step includes passing the array in the collapsedposition into the uterus and then expanding the array to the expandedposition.
 39. The method of claim 37, wherein the knit is stretchable,wherein the array is expandable from a collapsed position to an expandedposition and wherein the positioning step includes passing the array inthe collapsed position into the uterus and then expanding the array tothe expanded position, the expanding step causing the knit to stretch.40. The method of claim 37, wherein the providing step provides a knitcomprised of yarns of nylon and spandex plated with conductive material.41. The method of claim 32, wherein the providing step further providesthe array to comprise a bipolar array of electrodes and wherein thedelivering step delivers RF energy to the bipolar array.
 42. The methodof claim 32, wherein the applying step causes surrounding tissue wallsto at least partially collapse into contact with the array.
 43. Themethod of claim 32, wherein the method includes the step of passing aninsufflation gas through the tubular member to insufflate the uterus.44. The method of claim 43, wherein the insufflation step is performedprior to the applying step.
 45. The method of claim 43, wherein theinsufflation step is performed after the delivering step.
 46. The methodof claim 40, wherein the nylon yarns are plated with conductive materialand the spandex yarns remain unplated.
 47. The method of claim 46,wherein the spandex yarns provide the stretch and recovery of the knitand the plated nylon provides the conductivity of the knit.
 48. Themethod of claim 47, wherein the conductive material is comprised of acomposite layer of at least two different metals.
 49. The method ofclaim 48, wherein the metals are comprised of silver and gold.
 50. Themethod of claim 47, wherein the conductive material is comprised ofsilver.
 51. the method of claim 47, wherein the conductive material iscomprised of gold.